Artificial turf systems (also known as synthetic grass fields) have become a popular alternative to a natural grass field. These artificial turf systems typically include fibers tufted through a backing material and a particulate infill disposed on top of the backing material and in between the fibers.
Generally, there are two types of fibers that are commonly used in such artificial turf systems: monofilament fibers; and, slit film fibers.
The monofilament fibers are comprised of a single strand of material. The material is extruded through a spinneret to create a single strand (or multiple individual strands out of a single spinneret). After cooling, the strand is stored on a bobbin until it is ready to be tufted into a backing material. Typically, multiple strands are tufted together to the backing material in a group of fibers commonly referred to as a “tuft.”
The strand can have a variety of shapes and geometries including, flat, round, bat-wing, spined, or other known geometries. Since the monofilament fibers can be extruded in a variety of known geometries, it is believed by some that the monofilament fibers have a more natural look and increased structural integrity.
Inasmuch as the monofilament fibers are individually produced, attaching the tufts of individual monofilament fibers to a backing material can be complex—especially if compared with attaching a slit film fiber to a backing material.
Further, when using monofilament fibers, many manufacturers produce a finished product having a lower tuft bind strength than what those manufacturers may have obtained had they used slit film fibers.
These potential drawbacks may be a result of the adhesive coatings typically applied over the tufts on the underside of the backing material. This adhesive is used to secure/bind the tufted monofilament fibers in place. Since each tuft is comprised of a plurality of individual monofilament fibers, the coating material may have difficulty penetrating into the various interior spaces between some of the individual fibers. This can result in not all of the individual fibers actually being secured to the backing material, and thus, the resulting turf may have a lower tuft bind strength.
Unlike monofilament fibers, slit film fiber is typically extruded into a broad flat sheet which is cut into thinner strips and then fibrillated, and which then may be stored on a bobbin. The individual strips are tufted through the backing material. After the infill is installed, the strips are mechanically brushed so that the ends of the strips above the backing material are partially separated and, from the top of the artificial turf system, appear to be tufts of monofilament fibers.
In order to ensure that the slit film fibers are relatively durable and not abrasive, the extruded sheet must either be subjected to a biaxial stretching process or comprised of a high price linear low density polyethylene (LLDPE). Both of these options for producing acceptable slit film fibers are costly—which may add to the overall cost associated with the artificial turf system.
In sheet extrusion, the flow at the center of the sheet is much different compared to the flow at the outer area of the sheet. This creates a non-uniform product relative to strips made from the outer area of the sheet when compared to strips made from the center of the sheet.
In addition, because the slit film strands are cut into thinner strips (which are stored on a bobbin), the manufacturing process is longer and the equipment larger when compared with a process and equipment for making a monofilament fiber.
In addition, although they are cut into thinner strips (usually having a width between 5-12 mm, this width is often too large for needles on a tufting machine. This increases the risk that the tufting needles will break during the manufacturing process. Accordingly to accommodate the large widths of the fibers in the needles, the fibers have to be twisted. This transfers the rectangular shape of the fibers into a round shape that can be effectively passed through a tufting needle. However, this twisting causes additional stress on the fibers (which is not desirable). Further, it is an additional step in the manufacturing process that requires additional machinery. Thus, it increases the time and costs associated with manufacturing artificial turf systems.
While these fibers and the methods of making same are suitable for their intended purpose, there remains a need for a fiber and method of making same that combines the benefits of the monofilament fiber and the slit film fiber.
The present invention is directed to resolving the above concern/issues.